Cells and Energy
• How does a cell obtain energy?
• How do some cells make food
molecules?
Cells and Energy
• cellular respiration
• glycolysis
• fermentation
• photosynthesis
Cellular Respiration
• Cellular respiration is a series of
chemical reactions that convert the
energy in food molecules into a usable
form of energy called ATP.
• Glycolysis, the first step in cellular
respiration, is a process by which
glucose is broken down into smaller
molecules. It occurs in the cytoplasm.
Cellular Respiration (cont.)
Glycolysis produces
some ATP
molecules and uses
energy from other
ATP molecules.
Cellular Respiration (cont.)
• The second step of cellular respiration
requires oxygen and occurs in the
mitochondria of eukaryotic cells.
• The smaller molecules made from
glucose during glycolysis are broken
down.
• Large amounts of ATP—usable
energy—are produced. Cells use ATP
to power all cellular processes.
Reactions in the Mitochondria
Fermentation
• Fermentation is a reaction that
eukaryotic and prokaryotic cells use to
obtain energy from food when oxygen
levels are low.
• Fermentation occurs in a cell’s
cytoplasm, not in mitochondria.
Fermentation (cont.)
Lactic acid is produced as waste during
lactic-acid fermentation. Carbon dioxide
and alcohol are produced as waste
during alcohol fermentation.
Fermentation (cont.)
How does a cell obtain
energy?
Photosynthesis
Photosynthesis is a series of chemical
reactions that convert light energy, water,
and CO2 into the food-energy molecule
glucose and give off oxygen.
photosynthesis
from Greek photo, means “light”;
and synthesis, means
“composition”
Photosynthesis (cont.)
• The chemical reactions of
photosynthesis are powered by light
energy.
• In the chloroplasts of plants, pigments
such as chlorophyll absorb light energy
• Chlorophyll absorbs all colors except
green light, which is reflected as the
green color in leaves.
Photosynthesis (cont.)
How do some cells make
food molecules?
Photosynthesis (cont.)
• When an organism eats plant material
it takes in food energy from the plant’s
glucose.
• An organism’s cells use the oxygen
released during photosynthesis and
convert the food energy into usable
energy through cellular respiration.
• Glycolysis is the first step in cellular
respiration.
• Fermentation provides cells, such as
muscle cells, with energy when oxygen
levels are low.
• Light energy powers the chemical
reactions of photosynthesis.
What does cellular respiration
convert the energy in food
molecules into?
A.
B.
C.
D.
ATP
glucose
lactic acid
carbon dioxide
Eukaryotic and prokaryotic cells
use fermentation to obtain energy
from what?
A.
B.
C.
D.
water
food
oxygen
pigments
What chemical reactions converts
light energy, water, and CO2 into
the food-energy molecule
glucose?
A.
B.
C.
D.
lactic-acid fermentation
cellular respiration
alcohol fermentation
photosynthesis
Do you agree or disagree?
7. ATP is the only form of energy found in
cells.
8. Cellular respiration occurs only in lung
cells.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
A cell is made up of
structures that provide
support and
movement; process
energy; and transport
materials into, within,
and out of a cell.
Lesson 1: Cells and Life
• The invention of the microscope led to discoveries
about cells. In time, scientists used these
discoveries to develop the cell theory, which
explains how cells and living things are related.
• Cells are composed mainly of water, proteins,
nucleic acids, lipids, and carbohydrates.
Lesson 2: The Cell
• Cell structures have specific functions, such as
supporting a cell, moving a cell, controlling cell
activities, processing energy, and transporting
molecules.
• A prokaryotic cell lacks a nucleus and other
membrane-bound organelles, while a eukaryotic cell
has a nucleus and other membrane-bound
organelles.
Lesson 3: Cellular Material
• Materials enter and leave a cell through the cell
membrane using passive transport or active
transport.
• The ratio of surface area to volume limits the size of
a cell. In a smaller cell, the high surface-area-tovolume ratio allows materials to move easily to all
parts of a cell.
Lesson 4: Cells and Energy
• All living cells release energy from food molecules
through cellular respiration and/or fermentation.
• Some cells make food molecules using light energy
through the process of photosynthesis.
Which of these store energy, provide
structural support, and are needed
for communication between cells?
A. sugars
B. lipids
C. proteins
D. carbohydrates
What are the membranesurrounded components of
eukaryotic cells that perform
specialized functions?
A. cell walls
C. ribosomes
B. DNA
D. organelles
What is the term for the movement
of substances from an area of
higher concentration in a cell to
an area of lower concentration?
A. active transport
B. osmosis
C. diffusion
D. passive transport
Which of these describes the
process during which a cell takes in
a substance by surrounding it with
a cell membrane?
A. endocytosis
B. osmosis
C. exocytosis
D. diffusion
Pigments like chlorophyll absorb
light energy during which
process?
A. endocytosis
B. active transport
C. photosynthesis
D. osmosis
Which part of a cell contains
genetic information?
A. nucleic acids
B. amino acid molecules
C. proteins
D. carbohydrates
What is the fluid inside a cell that
contains salts and other
molecules?
A. protein
B. water
C. cytoplasm
D. flagella
What does facilitated diffusion
require to pass molecules
through a cell membrane?
A. water
B. glucose
C. light energy
D. transport proteins
During which process do cells take
in needed nutrients from the
environment through carrier
proteins?
A. endocytosis
B. active transport
C. exocytosis
D. passive transport
What type of fermentation do
some types of bacteria and yeast
use to produce ethanol and CO2?
A. alcohol fermentation
B. lactic acid fermentation
C. yeast fermentation
D. molecular fermentation